Method for drying glue and forming it into a continuous multi-layered sheet



Sept. 9, 1958 A H. ZEIGLER ET AL 2,850,769

METHOD FOR D RYING GLUE AND FORMING IT INTO A CONTINUOUS MULTI-LAYERED SHEET Filed June 25, 1954 dzfifal/ gvmvroas: BY ATTORNEX i atented Sept. 9, 1958 METHOD FOR DRYING GLUE AND F RMING IT INTO A CONTINUOUS MULTI-LAYERED Albert H. Zeigler, Wilmette, and George P. Goetz, Chicago, Ill., assignors to Armour and Company, Chicago, 11]., a corporation of Illinois Application June 25, 1954, Serial No. 439,340 3 Claims. (CI. 18-57) This invention relates to a method for drying animal glue and forming it into acontinuous multilayered sheet.

In Patents No. 2,556,247 and No. 2,556,954 a general method of drying animal glue and forming it into a continuous sheet is described, and the present application discloses an improvement on the method described in these patents. In the industrial use of the process described in the cited patents, certain problems have developed to which the present invention provides a solution. While it is commercially practical to apply an aqueous animal glue liquor to an internally heated .drum to form a layer thereon, as described in Patents No. 2,- 556,247 and No. 2,556,954, and to remove the glue layer as a continuous sheet, some difficulties are encountered in the further processing of the glue sheet.

It is not practical to dry the glue sheet ,on the drum to the final desired moisture content, and therefore it is necessary to pass the glue sheet through a drying oven. An apron-type forced air oven has been found desirable, but this type of oven is a large and expensive piece of equipment. 7

Another disadvantage of the process described in the patents referred to above is that there is a definite limit to the thickness of the glue layer which can be built up on the drum and removed in a continuous sheet. This frequently results in the necessity of operating the oven dryer at less than capacity, and results in a final product of lower density than is desirable in packaging and shipping the glue product. 7

It is therefore a general object of this invention to provide a process for drying animal glue and forming it into a continuous sheet which substantially overcomes the problems discussed above. Further objects and advantages and new results will become apparent as the specification proceeds.

This invention is shown in an illustrative embodiment in the accompanying drawing, in which Fig. l is a vertical sectional view of apparatus which can be used in practicing the method of this invention, some of the elements which are well known in the art being shown in a somewhat simplified and diagrammatic manner; Fig. 2, a detail sectional view of the ascending portion of the conveyor belt leading to the oven dryer, showing the superimposed glue films thereon; and Fig. 3,

' a detail sectional view of a portion of the conveyor belt in the last stage of the oven dryer, showing the alteration in the structure of the glue films and their fusion into an integral sheet.

In one of its phases, this invention is concerned with a e h d f ying n mal glue n f g .it int .a sheet, comprising forming .a layer of animal glue on each of at least two rolls, removing the glue layer from each of said rolls as a continuous film, superimposing said films upon each other, and passing said superimposed films through a drying zone to produce a continuous multilayered sheet of dried animal glue. This method and the novel apparatus employed for practicing the method can United States Patent *Ofi'zice 2 be better understood by reference to Fig. 1 of the accompanying drawing.

In Fig. 1, there is shown two internally heated drying rolls 10 and 11 of the type described in greater detail in Patents No. 2,556,247 and No. 2,556,954. 'On the ascending side of each of these drying rolls there is provided the usual driven applicator rollers 12 and 13, which rotate through a pool of aqueous animal glue liquor contained in vessels 14 and 15. r

The glue layer deposited on each of the outer surfaces of rolls '10 and 11 is carried upwardly by the rotation of these rolls while being held against these rolls by air streams from blowers 16 and 17 and being dried by heat supplied from the steam within the hollow drying rolls. Vent hoods 18 and 19 are provided above rolls 1 0 and 11 respectively for removal of the forced air together with the evaporated water vapor.

Various other auxiliary equipment can be provided for use with the drying rolls as described in Patents No. 2,556,247 and No. 2,556,954. It will be understood that the present drawing is somewhat simplified in form for the purpose of more clearly presenting the distinctive elements and features of the :present invention.

The glue layers formed on drying rolls 10 and 11 are continuously removed therefrom by means of doctor knives 20 and 21. If desired, auxiliary heating and cooling means can be provided for use in conjunction with these knives, such as steam jets and air jets, as described in the patents cited above. The continuous films a and!) removed from the drying rolls are passed between calendar or chill rolls 22-23 and 2425. These rollers are preferably constructed of material so that the glue film preferentially adheres to one of each pair of the rollers, such as to the rollers 23 and 25. Means will also be provided for supplying a cooling fluid such as brine to one or both of the calendar rolls.

Knives 26 and 27 are respectively provided forremoving the glue films'a and b from calendar rolls 23 and 25. The separated films descend onto a conveyor 28, which in the illustration given has a continuous horizontal portion 29 and a continuous rising portion 30. 7

It will be noted that conveyor 28, drying rolls 10 and 1 1, and calendar rolls 2223 and 24;25 are arranged so that films a and b are continuously superimposed on conveyor 28, and are then moved along together by the conveyor to an apron-type forced air drying oven 31.

As described in Patent No. 2,556,954, it is possible to crinkle or corrugate the glue film as it is removed from the drying rolls, and the degree of crinkle can be regulated by the relative speeds of the calendar rolls and the tension applied to the film by the calendar rolls. This procedure is described in greater detail in Patent No. 2,556,954, and the'specific method of crinkling described therein does not form a part of the present invention. However, the forming of crinkled films has been found to have an important and unexpected advantage for the purposes of this invention, as will now be described. 7

When the glue films are crinkled prior to the superposition of the films, the corrugations or crinkles therein provide open spaces or passages between the adjacent surfaces of the superimposed films, which can serve a-s vent or escape passages for moisture during the further drying of the glue films in the drying oven. This is illustrated parascending conveyor portig'm 30. The spaces or passages between the glue films can be readily noted, such as passages 32 and 33. The contacting surfaces of the glue films are relatively dry and hard, and the body of the films has suificient rigidity to maintain its corrugated structure. Therefore, it is possible to subject the superimposed films to further drying without closing these passages, and this 7 permits their use as vent or escape passages for the evaporated water vapor. Also, the circulating air within the drying oven can move into these passages and thereby promote the drying operation. However, it has been found desirable to obtain a final product of greater density than that which would be obtained from the individual glue films, and this can be accomplished by fusing the glue films into an integral sheet, as will be subsequently described.

Oven 31, in the illustration given, is divided by partitions into three stages or zones 34, 35, and 36. Within each zone there is provided three vertically-spaced, horizontally-extending endless conveyors 37 which are arranged so that the superimposed glue films can pass continuously through each zone and from one zone to the next. The drying zones are also illustrated as provided with a plurality of fans 38 for circulating air through the zones, and it will be understood that means will be provided in each zone for heating the air to the desired temperature.

In the preferred embodiment of the present invention the drying zone should be divided into at least two stages. Further, the temperature of the air in the first of the stages should be below the temperatures at which the glue films tend to soften and fuse together, while the temperature in the second of the stages should be high enough to promote the fusion of the glue films into an integral sheet. For example, zones 34 and 35 of oven dryer 31 can be employed in this manner by proper temperature control, the exact temperature used depending somewhat on the type and test of the glue being processed. Good results can ordinarily be obtained with high test hide glue with air temperatures in the first zone (e. g., zone 34) of 110 to 120 F., and air temperatures in the second zone (e. g., zone 35) of 180 to 200 F. In the illustration given, zone 36 of oven dryer 31 can be operated at the same temperature as zone 35, or at a lower temperature as may be desired for cooling the glue sheet before it is discharged from the dryer. In any event, the desired result is to dry the superimposed films first at non-fusing temperatures and then at fusing temperatures. This permits the passages between the glue films provided by their crinkled character to be used as escape passages for the evaporated water vapor and to increase the contact of the drying air with the inner surfaces of the films. The use of fusing temperatures at a later stage achieves the result of uniting the films into an integral sheet, and thereby producing a denser product. The appearance of the fused films as they would appear in zone 36 of the dryer is illustrated in Fig. 3 of the drawing.

The fused multilayered glue sheet 39, after being discharged from the dryer 31, is preferably broken up into small pieces for convenience in handling and packaging. For example, the fused sheet 39 can be passed to a breaker 40 for the purpose of forming flakes which are discharged into a receptacle 41. The flakes can be subjected to further grinding if desired, and the product thus obtained will have a greater density for the same volume than products produced from single glue films.

It will be apparent that the method and apparatus of this invention are not limited to forming glue sheets from two superimposed glue films, but are adaptable for use in forming glue sheets from more than two films, or more generally, from a plurality of glue films.

This invention is further illustrated by the following specific example.

Example 1 Using equipment like that shown in Fig. l of the drawing, bone glue liquor of from 39 to 40% solids was simultaneously applied to two rolls. The one roll was heated internally with steam at a temperature of 226 F., and the steam temperature inside the other roll was 233.9 F. The moisture content of the glue sheet removed from the roll having the lower steam temperature was 22.5%, while that removed from the roll having the higher steam temperature was 18.1%. The glue sheets as removed were continuously superimposed on a conveyor and fed piggyback through a hot air drying oven. The first stage of the drying oven was maintained at about F., while the second stage of the drying oven was held at a temperature of about F. The two superimposed glue sheets fused together in the second stage of the drying oven and issued from the oven as an integral sheet. The fused glue sheet was then crushed.

While in the foregoing specification this invention has been described in relation to a specific embodiment thereof and many details have been set forth in connection with this embodiment, it will be apparent to those skilled in the art that the invention is susceptible to other embodiments and that many of the details set forth herein can be varied considerably without departing from the basic concepts of the invention.

We claim:

1. The method of drying animal glue and forming it into a sheet, comprising forming a layer of water-containing animal glue on each of at least two rolls, removing the glue layer from each of said rolls as a continuous film, crinkling said layers to form corrugations in said films, superimposing said corrugated films upon each other to provide passages therebetween, and drying said superimposed films in at least two stages, the temperature of the first of said stages being below the temperatures at which said glue films tend to soften and fuse together, and the temperature in the second of said stages being high enough to promote the fusion of said films into an integral sheet.

2. The method of drying animal glue and forming it into a sheet, comprising forming a layer of water-containing animal glue on each of at least two rolls, removing and crinkling the glue layer from each of said rolls to provide continuous crinkled glue films, superimposing the crinkled glue films to form a multilayered sheet with passages between the layers, heating said multilayered sheet at a temperature adapted to evaporate water therefrom without softening said layers so that water vapor can escape through said passages, and then heating said multilayered sheet at a temperature adapted to soften said layers and to fuse them together to form an integral sheet.

3. The method of drying animal glue and forming it into a sheet, comprising forming a layer of water-containing animal glue on each of at least two rolls, removing the glue layer from each of said rolls as a continuous film, crinkling said layers to form corrugations in said films, superimposing said corrugated films upon each other to provide passages therebetween, and drying said superimposed films in a plurality of stages, the temperature of at least the first one of said stages being below .the temperature at which said glue films tend to soften and fuse together, whereby said passages remain open for the removal of water vapor therethrough.

References Cited in the file of this patent UNITED STATES PATENTS 2,252,585 Swanson et al Aug. 12, 1941 2,328,078 Kugler Aug. 31, 1943 2,345,013 Soday Mar. 28, 1944 2,556,954 Zeigler et al. June 12, 1951 

